I cant remember to be honest,the exact reasons anyway,but i know that it is not good to constantly ingest pure glycerin and that there were many downsides to glycerin.
If you want an excellent tincture powder an ounce of bud and 1 fl oz of olive oil and heat very very gently for 10 minutes stirring constantly.
Pour your mixture into you chosen jar or vials and shake the shit out of it and then pour it through a good tea strainer.
Then your ready to go.
Glycerin is basically just a shit weak alchohol that takes ages to extract the thc from weed and i do remember that it can cause mouth ulcers and stomach ulcers from ingesting to much neat glycerin.
Vodka would be a better choice and quicker.
.......ulcers........
threw it away.
could you imagine mouth ulcers? fuckin' gross.